Neutral endopeptidase 24.11 (enkephalinase, EC 3.4.24.11) is a member of the zinc protease family, and is the primary enzyme implicated in the degradation of the opiate peptides, Met-enkephalin and Leu-enkephalin, and also of atrial natriuretic factor (ANF). Because of the biological significance of enkephalinase, there has been considerable effort in designing potent inhibitors of the enzyme. We propose a novel strategy for the suicide inhibition (mechanism-based inactivation) of enkephalinase using specifically targeted peptidomimetics and peptides based on two design principles: 1) incorporating structural motifs which interact with the enzyme's S1' and S2' subsites using information obtained from enkephalinase substrate specificity and competitive inhibition studies, and 2) introducing latent functional groups, determined from our investigations of carboxypeptidase A, in these molecules which, upon masking, will inactivate the enzyme. The success of this approach will lead to the development of new antinociceptive and antihypertensive therapeutic agents. For Phase I of our study, we will synthesize derivatives of (R)-2-benzyl-5- cyano-4-oxo-pentanoic acid, and N-(cyanoacetyl)-L-phenylalanine, which incorporate the latent alpha-cyanocarbonyl moiety. These compounds will then be evaluated for their time-dependent inactivation of enkephalinase to test the efficacy of the approach.